British Pat. Specification 1,591,137 discloses polymer mixtures which comprise a polyphenylene ether, a block copolymer, and an aromatic phosphate. These known polymer mixtures comprise 60-99 parts by weight of polyphenylene ether, 40-1 parts by weight of block copolymer, and 1-40 parts by weight of aromatic phosphate. The known polymer mixtures are formed to articles by injection moulding. The polymer mixtures have good fire-retarding properties, a good impact strength, and the articles formed therefrom have a shining surface. The known polymer mixtures are too rigid for use as a cable sheath.
EP-A-124 916 discloses polymer mixtures which comprise 50-70 by weight of polyphenylene ether, 25-45 parts by weight of block copolymer, 10-20 parts by weight of phosphate compound, 2-10 parts by weight of mineral oil, and 0-10 parts by weight of additives. These polymer mixtures are suitable to form therefrom a wire envelope by means of wire sheath extrusion. The fire-retarding properties and the flexibility of these polymer mixtures are satisfactory for a wire envelope. For a cable envelope a material having better fireretarding properties and a greater flexibility is required.
EP-A-0135124 discloses flame retardant mixtures of a polyphenylene ether resin, an alkenylaromatic elastomer, an organic phosphate flame retardant and a crosslinking agent. Said mixtures are curable by heating or by exposure to high energy. Said mixtures can be used for the insulation of electrical wires and cables. The mixtures specifically disclosed comprise 10-12% by weight of phosphate, 30-37% by weight of polyphenylene ether, the remainder being mainly an elastomeric component.